The present invention relates primarily to the construction of product display packages although it can have other applications. More particularly, the present invention is directed to providing printed substrates made of paper, cardboard, plastic and the like with transparent thermal adhesive surfaces to which items may be readily adhered. Such items may include, for example, transparent plastic containers for products to be displayed in their packages.
Prior art transparent containers which hold products are applied to backing cards by using a sandwich of two overlapping cards into which a window has been cut in one or both of the panels. A plastic container having integral flanges is then placed in the window with the flanges sandwiched between the overlapping card panels which are cemented together. Although it is know to produce web materials which have thermosetting adhesive surfaces, until now, their application has been limited to serving as outer layers for packages for security and aesthetics.
Referring to FIG. 1 of the drawings, it is known to coat a web of paper, cardboard, plastic or similar stock 1 with an adhesive 3, either a liquid drying one or a molten extrusion. Thereafter a web of plastic film 5 is layered over the adhesive to form a laminate of the paper, cardboard, plastic or similar stock and the web of plastic film. Next an extrusion of a molten thermal adhesive 7 is coated onto the surface of the plastic film to provide a laminate 9 having a paper, cardboard, plastic or similar material substrate and a thermal adhesive surface 11.
The prior art process by which thermal adhesive is applied requires that the thermal adhesive material be heated to above its melting point and layered onto a continuous web fed at a uniform rate between a supply spool and a takeup spool without starting and stopping or otherwise upsetting the rate of travel of the web as the coating of molten thermal adhesive is uniformly applied. The laminate 9 can only be produced from web materials which are conveyed through a process line wherein the adhesives and plastic film are assembled.
In some applications it is desired to print relatively small sheets of paper, cardboard, plastic or similar material and thereafter apply a thermal adhesive to the printed surface. Such printed sheets cannot be treated in a web conveyor apparatus. Nor can a molten thermal adhesive be applied to single sheets of paper, cardboard, plastic or the like.
Referring to FIG. 2 of the drawings, it is also known in the art to produce plastic film material in rolls onto which a thermal adhesive has been coated in a manner similar to that shown in FIG. 1 but without the paper, cardboard, plastic or similar material substrate. A laminate of plastic film material 13 coated on one side with a thermal adhesive has been found useful for enhancing the appearance and strength of containers used in product packaging. In such applications, the plastic film laminate 13 is applied to a package 15 made of paper, cardboard, plastic or similar stock with the thermal adhesive side of the plastic film 13 against one or more of the panels which form the package. After the laminate 13 is adhered to the package by application of heat, the opposite uncoated side of the plastic film provides a glossy, satin, or matte (depending of the film surface) look and feel to the package which makes it aesthetically attractive and resistant to tearing.